Iphone 4: After ios 6.1.3 update phone will not connect to home wifi "unable to join the network"

Well done on solving your problem.

But with all due to respect to you and the others that come here and say "the following solved my problem" the sad fact is (and it IS fact) that there is an issue with iOS 6.1.3 that has broken WiFi for many people. Some of those many people have managed to get things working again - that does NOT mean that the problem doesn't exist. It DOES.

I am one of the lucky ones whose wifi worked again by reassigning channels on the routers. Others are finding different workarounds. But that is what they are - there is still an inherent software related issue in going from 6.1.2 to 6.1.3 that causes many people issues with their WiFi.

I am also aware of those Apple die-hard fans who find it hard to believe that this is true. Get a grip and think about how irrational your arguments are in the face of the empirical evidence that is the 6.1.3 'upgrade'.

I have exact same problem. Found that only turning phone off and then back on did the wifi switch back on. But now even that won't work and wifi in "settings" is greyed out. Can I restore to previous iOS version?